HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer[http://www.apple.com] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, which increased performance and lowered fragmentation [http://developer.apple.com/technotes/tn/tn1121.html#HFSPlus]. It also implemented Unicode (rather than Mac proprietary formats) for naming files.

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HFS+, or Hierarchical File System Plus, is the file system designed by [http://www.apple.com Apple Computer] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, which increased performance and lowered fragmentation (See: Technical Note TN1121). It also implemented Unicode (rather than Mac proprietary formats) for naming files. HFSX is a variant of HSF+ that is case sensitive.

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There are structurally many differences between HFS and HFS+, which are listed below[http://developer.apple.com/technotes/tn/tn1150.html#HFSPlusBasics]:

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There are structurally many differences between HFS and HFS+, which are listed below (See: Technical Note TN1150).

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Apple technical notes are available for the HFS+ file system from their [http://developer.apple.com/cgi-bin/search.pl?q=HFS+&num=10&site=default_collection website].

Apple technical notes are available for the HFS+ file system from their [http://developer.apple.com/cgi-bin/search.pl?q=HFS+&num=10&site=default_collection website].

Latest revision as of 14:58, 8 April 2013

HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, which increased performance and lowered fragmentation (See: Technical Note TN1121). It also implemented Unicode (rather than Mac proprietary formats) for naming files. HFSX is a variant of HSF+ that is case sensitive.

There are structurally many differences between HFS and HFS+, which are listed below (See: Technical Note TN1150).

Feature

HFS

HFS Plus

Benefit/Comment

User visible name

Mac OS Standard

Mac OS Extended

Number of allocation blocks

16 bits worth

32 bits worth

Radical decrease in disk space used on large
volumes, and a larger number of files per volume.

Maintains efficiency in the face of the other
changes. (This larger catalog node size is due to
the much longer file names [512 bytes as opposed to
32 bytes], and larger catalog records (because of
more/larger fields)).

Maximum file size

231 bytes

263 bytes

Obvious user benefit, especially for multimedia
content creators.

An HFS+ volume contains five special files:

Catalog file - Describes the folder and file hierarchy of the volume. It is organized as a "balanced tree" for fast and efficient searches

Extents overflow file - Additional extents (contiguous allocation blocks allocated to forks) are stored in a b-tree in this file

Allocation file - Specifies whether an allocation block is free (similar to $Bitmap in NTFS). This is stored in a bitmap, specifying a free allocation block with a "clear bit"

Startup file - Allows computers to boot that do have built in support for HFS+ file systems

HFS+ also implements journaling, which allows fast recovery in the case of a crash or power outage. According to Apple, "The purpose of the journal is to ensure that when a group of related changes are being made, that either all of those changes are actually made, or none of them are made."[1]

Apple technical notes are available for the HFS+ file system from their website.